DESCRIPTION: This project focuses on the structural requirements for the induction of micro satellite instability using DNA polymerases, auxiliary proteins, and templates that contain triplet repeats. The goal is to determine which structures enhance expansion of repetitive sequences using model in vitro and in vivo systems. The studies on DNA polymerases will be coupled with the effects of the FEN-1 nuclease and with in vivo studies using the E.coli SURE cells. Finally, studies using computer simulation for analysis of the structures will be carried out to provide insights into the studies with purified DNA polymerases.